A source at the Elysée palace said secret services were "investigating a Chinese link" in the scandal after the company suspended three senior executives for allegedly committing "very serious faults".

All three were working on Renault's high-profile electric car programme and one as a member of the company's management committee.

If the allegations were confirmed, it would be one of the biggest and most potentially damaging cases of commercial espionage in recent years.

Tonight a French magazine claimed the three men had leaked information about the development of batteries for the electric vehicles that Renault hopes to put into production in the next 18 months.

Le Point said the employees had been approached by a private company used as a subcontractor by Renault. It claimed that in return for information, money had been paid into foreign bank accounts.

More damaging for Renault, Le Point also alleged the leaked information concerned multi-million euro technology that the company had yet had a chance to patent, meaning it was not protected from being copied.

However, one of the accused men, Mathieu Tenenbaum, was reported to be "stunned" by the allegations and said he was waiting to hear details of the accusations against him. His lawyer, Thibault de Montbrial, told AFP that the deputy director of the electric vehicle programme was thrown out of the Renault building "in a matter of minutes with no justification apart from a laconic and enigmatic 'we know what you have done, you should admit it'."

"This gulf between the silence of his bosses on Monday and the pre-declaration of his guilt in the public communication by Renault for the last four days has left him puzzled."

Renault has refused to comment after suspending the three employees and has not confirmed reports it plans to take legal action against them.

The government has warned of an "overall risk" to French industry. Renault is 15% owned by the French state.

Bernard Carayon, an MP for the ruling UMP and a specialist in economic intelligence, said the Chinese connection was being taken seriously.

"The suspicions are effectively going that way," he told Le Figaro.

He added: "This scandal rests on a lack of sufficient preventive measures especially when certain state services, in particular the DCRI [Direction Centrale du Renseignement Intérieur, the French intelligence services] are in a position to give technical advice at a high level to companies."

Renault is France's biggest car-maker and, with a workforce of 54,300 in France and a total of 122,600 worldwide, is a key player in the country's economy.

The three suspended staff worked at the Technocentre at Guyancourt, 20 miles from Paris, where company engineers work on coming up with new models.

Renault, and its Japanese partner Nissan, has invested €4bn in developing electric vehicles and plans to put three models on sale this year and a fourth next year. "The group [Renault] is worried about its electric programme and hopes its advance in this technology won't be threatened," a source told Le Figaro.

China is promoting ecological vehicles as part of the development of its car industry and its output is expected to reach 1m units by 2020, according to a Beijing official. Vehicle emissions account for 70% of air pollution in major Chinese cities.

A member of the DCRI told Le Point that French companies had underestimated the potential damage of industrial spying: "French companies don't have a sense of economic intelligence," he said.

He added: "This is a classic case of spying. The Chinese are masters of this and they've gone on the offensive."